California FTB wants to tax my Father who is a Florida resident

I am a resident of California for many decades.  My Father is a resident of Florida for many decades.  I handle my Father's legal and financial affairs because he is no longer able to due to cognitive decline.   A "FILING ENFORCEMENT SECTION MS F180" notice from the California FTB was sent to my Father at my California address for the tax year of 2019. 

 

My Father lives at an assisted living facility in Florida since 2017.  It is best that financial documents come to me and not to my Father.  I opt for e-delivery whenever possible, but I have specified my California address for a couple of my Father's financial accounts and his Florida retirement pension to ensure I can receive tax related documents.  So I suspect that CA FTB gained access to 1099R and 1099-Div forms for my Father that had my California address on them and decided that my Father should be paying California taxes.

 

The California FTB is now demanding that “questionnaire FTB 4600B ENS” be filled out and that my Father’s federal tax return, all withholding statements and proof of IRS tax payment be sent to them.  If this is not done, they will assess California income taxes and penalties.

 

"FTB 4600B ENS" is a complicated questionnaire.  I prefer to not provide the California FTB with detailed tax return information.  I’m afraid this will make them even more interested in taxing my Father.  The real issue that needs to be documented is why my Father is not a California resident.  So I have a few questions.

 

I’m looking for the simplest, trouble free resolution to this issue.  Any advice on how to best fill out this questionnaire to ensure the issue is quickly resolved?

 

What is the best way to document that my Father domicile is Florida and not California?

 

Can I avoid sending detail tax and income information to California FTB?

 

Should I get professional representation for this issue?